1. Field of the Invention
This invention relates generally to railway vehicle coupler assemblies and more particularly to an improved method for producing a coupler and an improved coupler.
2. Brief Description of the Related Art
Railway couplers, particularly those utilized for railway freight cars or vehicles have a coupler body which is an integral casting of a coupler head and a shank. The head of the shank may be an AAR Standard Type “E” or “F” Coupler Head. The head also carries a knuckle and includes a lock, a thrower, a pivot pin and an articulated lock assembly. The coupler is made from a casting formed from low alloy steel. Although there are AAR standards for couplers, the length of the shank from the butt end of the coupler to the location where the shank joins the head may vary. The coupler is designed to be installed on a draft yoke of a railway vehicle. The butt end of the coupler shank is a spherical surface and bears against the face of the front follower of the yoke. The coupler is pivotally mounted on a yoke with a pin that joins the coupler to the vehicle's draft yoke.
Railcar couplers are disposed at each end of a railway car to enable joining one end of such railway car to an adjacently disposed end of another railway car. Couplers generally carry a knuckle which is pivotally mounted on the coupler head and is designed to engage with another knuckle carried on an adjacent coupler or another car.
Typically, couplers are heavy shafts that extend from each rail car. Generally, each coupler is engaged with a yoke housing a shock-absorbing element referred to as the draft gear. The type-E coupler is the standard coupler for railway freight cars. The type-E coupler has standard specifications such that producers making a type-E coupler adhere to a standard specification, so that the standard railway car couplers are completely interchangeable, regardless of the manufacturer. In addition, adherence to a standard also enables couplers from any one manufacturer to be able to be readily joined to couplers from any other domestic manufacturer. The Association of American Railroads (“AAR”) has adopted standards for railway couplers. The coupler must include specific geometry and dimensions that allow it to receive a knuckle, and the geometry must be such that the knuckle is allowed to freely operate when coupling and uncoupling railway cars. These dimensions and features of the coupler may be checked for compliance with AAR standards by using gauges, which are applied to the coupler to verify the coupler dimensions or parameters are within an allowable variation or tolerance range.
Couplers have a particular life, and in instances may fail. In many cases when a railcar coupler fails, a replacement coupler must be carried from the locomotive at least some of the length of the train, which may be up to 25, 50 or even 100 railroad cars in length. The repair of a failed coupler can be labor intensive, can sometimes take place in very inclement weather and can cause train delays.
The production of couplers involves a method known as sand casting or “green sand” method, where a flask which is a box having an open top and open bottom, is filled with sand around a pattern which is a component (such as a wood piece) that is used to make the impression in the sand. The green sand casting process involves a number of components and steps, as a flask or box must be created with cope and drag sections, so that the pattern may make an impression in the sand and can be removed from the mold prior to introduction of the molten metal therein. A mold may include additional components, such as, for example a gate and one or more runners through which the molten metal is admitted to one or more parts of the impression formed by the pattern. Gates and runners generally are formed similar to the mold impression, for example, with a component, such as wood (e.g., a gate and runner pattern), and are removed prior to the introduction of the molten metal, often with the removal of the pattern. A path of entry, such as an opening for admission of molten material is generally made through a sprue which is a communication path leading to the gate. The gate generally receives the molten metal that is poured through the sprue opening, and the runners act as conduits through which the molten metal flows to the impression or mold space formed by the pattern. In the case of forming a coupler, the mold must further be provided with cores. Cores are generally made from a material that remains present in the molding process during the mold melt introduction and are removable thereafter. In some cases, the configuration of the pattern or ultimate coupler part does not allow for removal of a core in its solid form, so it must therefore be broken apart and removed in pieces. The cores generally also may be made from green sand. The “green sand” method involves baking the mold so that the sand will form a mass and stay together during the molding process, and, in particular, when the molten metal is introduced into the mold. Once the molten metal is introduced into the mold through the sprue, gate and runners, the molten metal flows around the open areas of the mold and is blocked from entry to areas of the mold that are occupied by cores. The placement and positioning of cores in the mold, as well as the ability for a core to remain in place is required in order to produce a usable coupler. Although attempts are made to secure the core in a proper position, the cores have been known to shift prior to or during receiving the melt. In instances where a core shifts or where the green sand is not completely amassed together (e.g., where portions break off leaving fractured or missing edges), the coupler produced may need to be scrapped.